Shiva appeared as Lingodbhavamurti – a linga form with no
beginning and end – before Vishnu and Brahma. Lingodbhavamurti is represented
as a cylindrical pillar of fire with the image of four-armed Shiva seen inside
in the center of the linga. In some murtis, Brahma and Vishnu are also shown.
In some they are represented by swan and boar.
Legend has it that Vishnu and Brahma wanted to know who was
superior and this led to a fight. Lord Shiva intervened and said whoever can find
out the origin or end of Shivling is superior. Lord Shiva appeared before them
in the form of a huge pillar of fire - Lingodbhavamurti. Lord Vishnu went down
searching and Brahma went up searching. Both traveled and traveled but never
met the beginning or end.
After the futile search, Lord Vishnu and Brahma prayed to
Shiva and appeared before them in the form of Jyotirlinga and this day of the
appearance of Lord Shiva is celebrated as Shivratri.
Lingodbhavamurti form of Shiva can be found in the walls of
Shiva Temples in Tamil Nadu especially at the Kailasanatha Temple